1. Field of the Invention
The subject invention relates to compression-type spray devices having means for regulating both the composition and the force of the spray. More particularly it is concerned with regulated compression-type devices capable of use with materials having a wide range of density, composition and particle size.
2. Prior Art
It has long been recognized that by varying the proportions of air and fluid or particulate material in a compressed air-produced spary stream it is possible to control the composition and force of the resulting spray and to permit the spraying of materials having a variety of flow characteristics.
However, most such prior art sprayers, and particularly those of the inexpensive, hand-operated type, have required a change of nozzel to accommodate materials of greatly different flow characteristics. Generally, each nozzle has been capable of handling a limited change of materials.
Sprayers having adjustable nozzles have also been characterized by objectionable "touchiness" or over-sensitivity of the spray dynamics to the mixture control, at least in some part of its range of adjustment. Prior art attempts to overcome these problems have introduced nozzles with complex machined or cast shapes, or utilizing deformable rubber or plastic sealing parts, to provide acceptable dynamic range and reasonably consistent response sensitivity over the range of adjustment.
In one representative example, the variable spray device of L. W. P. Buchanan, described in U.S. Pat. No. 1,670,235 (May 15, 1928), features nozzle adjustability for controlling the texture of the spray, but also provides a choice of replaceable nozzles (40 and 40a of Buchanan's drawings). It should be noted that adjustment of Buchanan's nozzle controls only the injection of air into the final nozzle orifice, although the material supply is controlled to some extent by the application of pressurized air at the end of the supply tube.
In another example, the nozzle assembly for sprayers, patented Feb. 2, 1960 by A. H. Pinke (U.S. Pat. No,. 2,923,481), provides a camming action to close and open the nozzle as a whole. In other words, the adjustment of the nozzle controls the material supply and pressurized air in common. Again, the relative proportions of the two are controlled to some extent by the application of pressurized air at the end of the supply tube, which is perhaps more effective when the nozzle is closed. (Pinke also provides an O-ring closure to seal off the nozzle entirely, rather than relying on metal-to-metal closure as with Buchanan.)
In an attempt to control more directly the proportions of air and material supply, Howard V. Jett and Joseph V. DeMarco patented June 28, 1974 an aggregate spray gun (U.S. Pat. No. 3,820,722), whose nozzle adjustment acts only on the pressurized air supply to the mix. Thus as with Buchanan the proportions of air and material supply are adjusted by manipulating the nozzle. In addition Jett and DeMarco apparently attempt to overcome the problems of consistent sensitivity over the range of the nozzle adjustment by providing an adjustment mechanism in which manipulation of the nozzle compresses on 0-ring against a fluted internal surface consisting of an internal cone followed by an internal cylindrical surface. The deformation of the O-ring into the compound channels produced by the fluting of the internal cone and cylinder presumably offers a degree of control superior to that of Pinke or Buchanan.
None of these devices is addressed to the desirability of or succeeds in, providing for the use of the sprayer with a wide range of materials. Neither is any of them capable of smooth, consistent sensitivity to adjustment over the entire region of adjustability of the nozzle.
It is the principal object of the subject invention to provide a simple, inexpensively constructed, easily maintained adjustable spray device which overcomes these deficiencies.